Plating rack with plural layer plastisol coating



Dec. 16, 1969 L. B. SPERRY PLATING RACK WITH PLURAL LAYER PLASTISOLCOATING Filed June 12, 1967 INVENTOR. 11474 6'. 8/ 559) United StatesPatent 3,484,361 PLATING RACK WITH PLURAL LAYER PLASTISOL COATING LymanB. Sperry, 1561 Groton SE., Grand Rapids, Mich. 49506 Filed June 12,1967, Ser. No. 645,327 Int. Cl. C23b 5/70 US. Cl. 204297 5 ClaimsABSTRACT OF THE DISCLOSURE A rack having a cured plastisol insulatingcoating, The rack is initially dipped into a relatively flexible plasticforming plastisol and, after partial curing, those portions of the rackordinarily subjected to brading forces during use are re-dipped into arelatively hard plastic forming plastisol. The layers are fully curedsimultaneously in the preferred embodiment of the invention. Theflexible plastisol covering usually the upper portions of the rackpermits flexing of the article retaining members without fear ofcracking the insulating coating. The hard plastic insulating layercovering usually the lower portion of the rack prevents abrading of theinsulation when the rack is slid across or bumped against the floor.

BACKGROUND This invention relates to plating racks and, moreparticularly, to racks covered with an insulating or otherwise inertmedium to prevent depositing of metal or the like there onto during use.

In the fabrication and utilization of article retaining racks such asare utilized to retain and suspend articles within plating baths,anodizing baths and the like for electro-chemical or other types ofsurface treatment, it is usually desirable that the rack be covered withsome type of inert insulating material. In the case of electro-chemicalprocesses, of course, those points where the rack electrically connectsto the individual articles and the power supply are not covered. Theinert insulation serves a number of purposes, depending upon theparticular type of environment. For example, it prevents the plating ofmaterial onto the rack as well as onto the articles during anelectroplating operation and, thus, results in a marked savings insofaras material costs are concerned.

In the past, racks of the type described have been insulated bypreheating them and dipping them into plastisol (polyvinyl chloride) oneor more times to build a coating of desired thickness. The rack is thensubjected to heat to cure the plastic coating so formed and, afterremoving the coating from the contact points, put into use.

Since most racks of the type described depend upon the flexibility ofthe article-engaging members to retain the articles thereon, theplastisols which have been utilized for insulating purposes shouldretain their flexibility so that they will not crack. The harderplastisol coatings crack much sooner in service than do the softercoatings. While such soft insulating coatings have proved satisfactoryinsofar ast he article-retaining members and other interior portions ofthe rack have been concerned, a marked tendency has existed for theinsulating coating to be scraped from portions of the racks such as thebottom when, for example, it is slid across the floor, bumped againstthe floor or otherwise subjected to abrading forces. When such scrapingoccurs, the rack should be repaired or recoated immediately in order toprevent the electro-deposition of plating or other treatment materialthereon. Such repair or replacement, of course, results in substantiallyincreased overhead to plating concerns electro-deposititon of plating orother treatment material thereon. Such repair or replacement, of course,results in substantially increased overhead to plating concerns as Wellas necessitating the obtaining and storage of extra racks which may bebrought into use immediately upon the removal of a scraped rack from theplating apparatus.

In addition to the problems incurred in electrolytictype treatment,insulative coatings of the type described also perform a desirablefunction in surface treatment methods which do not depend uponelectrolytic techniques for achieving the desired surface condition.Thus, for example, where the particular process involves the meresubjection of the parts to be treated to chemical reagents, the presenceof the plastic insulating coating on the racks ordinarily will preventinter-action of the reagent and the rack-forming metal and, in a mattersimilar to that discussed in connection with electro-plating, provide amore uniform product at a more economical price. Thus, regardless of theparticular type of surface treatment under consideration, if aninsulating coating on the rack is necessary for an economical andsatisfactory treatment of the parts, and if the rack depends upon theflexibility of certain portions thereof to retain the articles thereon,the prior art has used either a flexible or soft type of plastisol whichis easily scraped from the rack surfaces when they are subjected toabrading forces, or a hard" type of plastisol which is subject to earlycracking at points which require flexing.

Objects and specification It is an object of this invention, therefore,to provide a rack of the type described which is not subject to thedisadvantages outlined above.

More particularly, it is an object of this invention to provide a rackand coating therefor which, while permitting flexing of thearticle-retaining members Without cracking, is not subject to beingeasily scraped from the rack when it is bumped against or slid acrossthe floor or walls of the particular enclosure in which the plating orother type of treatment process is being executed.

Thus, it is an object of this invention to provide a rack of the typedescribed having a markedly increased life expectancy and, which may befabricated at a cost only slightly greater than that incurred in thefabrication of insulated racks in accordance with the teachings ofpresent technology.

These as well as other objects of this invention will be readilyunderstood with reference to the following specification andaccompanying figures in which:

FIG. 1 is a perspective vew of a typical plating rack;

FIG. 2 is a schematic illustration of the initial dipping process;

FIG. 3 is a schematic illustration of the final dipping process; and

FIG. 4 is a cross-sectional view taken along plane IV IV of FIG. 1illustrating the doublecoated, abrasionresistant section of the novelrack.

Briefly, this invention relates to an article-retaining rack having ametallic framework adapted to be suspended within a solution tank or thelike, the framework having a plurality of flexible article retainingmembers aflixed thereto and a plastic insulating material coveringsubstantially all surfaces thereof. The improvement comprises theutilization of a first insulating material to cover those portions ofthe rack including the flexible members not ordinarily subjected toabrading forces during use. This first material is sufficiently flexibleso as not to crack under the influence of the flexing of the retainingmembers. A second insulating material is utilized to cover thoseportions of the rack, such as the base thereof, which are ordinarilysubjected to abrading forces during use. The second material is harderthan the first material whereby it cannot be scraped easily from therack by the abrading forces.

Referring now to the figures, a preferred embodiment of this inventionwill be described in detail. FIG. 1 illustrates a typical plating rackto which the teachings of this invention are applicable. The rack,indicated generally by the reference numeral 10, comprises a pair ofvertical splines 11, an upper frame member 12, and a lower frame member13. Depending upon the particular environment in which the rack is to beutilized, the base thereof may be provided with guard stubs or the likeas is well-known in the art. As will be readily appreciated, theteachings of this invention are equally applicable despite suchvariations in the specific rack construction.

Suspended between the frame members 11 are a series of spaced horizontalcross bars 15. Aflixed to the cross bars 15 are a plurality of flexiblearticle retaining clips 16 upon which the articles are adapted to besuspended during the treatment of their surfaces. As is well-known inthe art, the clips 16 may take any of a wide variety of forms and areusually designed with the retention of a particular part in mind. This,of course, is true as regards the remainder of the rack structure and,for example, in many situations no horizontal crossbars 15 arenecessary, the articles to be treated being of sufficient size to beotherwise suspended from the rack. As will be apparent, the teachings ofthis invention will find applicability regardless of the physicalconfiguration of the particular rack. The rack illustrated in FIG. 1 ismerely a typical representation and its structural characteristics arenot meant to limit the scope of this invention.

The upper section of the rack has one or more supporting hooks 17affixed thereto. The rack and articles carried thereby are suspendedfrom hooks 17 within the plating or other treatment bath by means ofthese hooks. Where the particular operation involves electrolysis, theupper extremities of the hook 17 will ordinarily be left bare to providea conductive path from the support bar through the metallic portions ofthe rack to the articles. In this regard, the tips of thearticle-retaining clip 16 will ordinarily also be left bare such thatconductive contact is established between the article and the powersupply.

After fabrication of the metallic rack components by welding, rivetingor the like, the rack is preheated and dipped in a solution of flexibleplastic forming plastisol 24 which, as shown in FIG. 2, may be containedwithin a dipping tank indicated generally by the reference numeral 20.Merely by way of example, the rack may be supported from an overheadhoist 21 aflixed to the ceiling 23 by means of cable 22. The rack may bedipped into the flexble plastisol 24 a suflicient number of times withintermittent reheating, if necessary, to provide a gelled plastisollayer of desired thickness thereon. At this point, preferaly, the rackis moved above a shallow dipping tank, such as that indicated by thereference numeral 30 in FIG. 3, and the lower portion, after suitablepreheating, is dipped into a solution of hard or rigid forming plastisol31. Dipping may be repeated within tank 30 until a gelled layer ofdesired thickness has been placed thereon. The rack is then subjected toheat in an oven or the like to cure both the flexible and hardplastisols.

While the preferred embodiment illustrated above, contemplates thecuring of the two layers simultaneously, it will be apparent to thoseskilletd in the art that the first flexible layer might be cured priorto formation of the second layer if suitable bonding between layers canbe obtained. In either event, the process results in the coating of theinterior and upper sections of the rack including the flexiblearticle-retaining members 16 with a plastic which will remainsufficiently flexible to prevent cracking under the influence of theflexing article retaining members 16. The lower portion of the rack,particularly that portion constantly coming into abutment with the flooror the like, has a harder plastic insulating layer covering it. Theabrasion resistance of this layer prevents scraping of the material fromthe plating rack during ordinary usage and, thus, vastly prolongs itslife.

As shown particularly in FIG. 4, the lower sections of the plating rackindicated generally by the reference numeral 13 are covered both by thelayer of soft plastisol 24' and the layer of hard plastisol 31'. Duringcuring, these layers are curingly bonded together to provide a sturdyand highly functional assembly. That is to say, that the two gelledlayers of soft and hard plastisols are polymerized or curedsimultaneously in overlaying relationship with the metallic rackstructure and each other.

As noted, the plastisol 24 utilized for formation of the initialinsulating layer is flexible, preferably having a Shore A durometerhardness of to 80. The hard plastisol 31, utilized to cover thosesections of the rack which are subject to abrading forces duringordinary usage, has a hardness which, ordinarily, exceeds 85.

It will be noted that the plating rack which is the subject of thisinvention may be fabricated with little added expense and, yet, has alife expectancy greatly exceeding that of plating racks manufactured inaccordance with the teachings of the prior art. For example, it is notunusual to have to completely recover or reinsulate a plating rackcoated with a flexible plastisol only at intervals of three or fourmonths whereas, the plating rack which is the subject of this inventionwill, in all probability, never require reinsulating. The savings intime, trouble and money for the rack user are evident. This fact,coupled with the relative ease with which the additional coating stepmay be executed in the fabrication of the rack, is one of the salientfeatures of this invention.

While a preferred embodiment of this invention has been illustrated indetail, it will be readily apparent to those skilled in the art thatother embodiments may be conceived and fabricated without departing fromthe spirit and scope of this specification and the accompanyingdrawings. Such other embodiments are to be deemed as included within thescope of the following claims unless these claims, by their language,expressly state otherwise.

I claim:

1. In an article-retaining rack having a metallic framework adapted tobe suspended within a treatment material containing enclosure, saidframework having a plurality of flexible article retaining membersaflixed thereto and a plastic insulating material covering substantiallyall surfaces thereof, the improvement comprising a first layer ofinsulating material covering those portions of the rack including saidmembers not ordinarily subjected to abrading forces during use, saidfirst layer being sufliciently flexible so as not to crack under theinfluence of the flexing of said retaining members and a second layer ofinsulating material covering those portions of the rack ordinarilysubjected to abrading forces during use, said second layer being harderthan said first layer whereby it cannot be scraped easily from said rackby said abrading forces.

2. The rack as set forth in claim 1 wherein said first and second layersof materials are cured plastisols.

3. The rack as set forth in claim 2 wherein said first layer also coversthose portions of said rack ordinarily subjected to abrading forces,said second layer overlying said first layer.

4. The rack as set forth in claim 3 wherein said first and second layersare curingly bonded together.

5. The rack as set forth in claim 2 wherein said first layer has a ShoreA durometer hardness in the range of about 65 to 80 and said secondlayer has a Shore A durometer hardness exceeding about 85.

6 References Cited UNITED STATES PATENTS 8/1957 FOX et al 211-41 7/1962Belke 204-297 US. Cl. X.R. 117-75; 2l11l3

